The recovery of plastics from waste streams, such as from durable goods, is a considerable challenge due to the presence of several types of plastics as well as non-plastic contaminants. High purity particles recovered from a recycling process can be extruded and pelletized to make a high quality product. However, such extrusion can be difficult and the quality of the product can be poor unless certain types of contaminants are reduced to very low levels prior to extrusion.
Such problematic contaminants include, among others, non-plastics such as wood, particle board, paper, cardboard, rubber, textiles, metallic coatings, wires and circuit boards. Because such materials do not melt, they can quickly result in a blockage of the melt filtration equipment used during the extrusion step, even when these contaminant materials are present in small amounts. Non-melt particles smaller than the size of screens used in the melt filtration equipment can pass through the melt filtration equipment, but can result in cosmetic and/or mechanical defects in products made out of the recovered plastics. In addition, cellulose-based contaminants (e.g., wood, particle board, cardboard and paper) can start degrading at some typical extrusion temperatures, so dark specks of degraded material can disintegrate from the original contaminant particles and pass through the melt filtration equipment. In addition, some plastics contain coatings such as metallic paint or metal plating that can cause similar difficulties in the extrusion step and in the products from extrusion of recycled plastics.